1. Field of Invention
The invention relates to valves and more particularly to rotary valves.
2. Discussion of Related Art
Valves are used to control the flow of fluids, such as air or water, or solids, such as powders, and typically include a seal component that covers a flow port through the valve. To provide an adequate seal, valve designers strive to create a relatively tight fit or seal between the seal component and the port, and this may be accomplished with relatively large biasing forces acting on the seal component. However, such a high biasing force must be overcome when it is desired to actuate the valve, resulting in a relatively high energy cost.
Many common valve applications, such as poppet valves used in internal combustion engines, could benefit from a reduction in efficiency losses. Efforts have been made to employ rotary valves in engines, which require less energy to actuate than poppet valves and offer additional advantages, such as allowing the engine to operate at a higher rpm, allowing for the use of variable valve timing, and providing fewer parts. However, these rotary valves have not gained widespread use, in part because the operating efficiency gain over conventional poppet valves is not significant, thermal expansion is difficult to manage, cost is relatively high, and acceptance by automotive engine designers has been low. Improvements to valves and rotary valves in particular have largely focused on material selection that only slightly reduced these deficiencies including frictional losses while maintaining or improving the sealing characteristics.